Synthesis of lipids and acetylcholine from acetyl-CoA in the mammalian brain are cytosolic processes. Since the main organelle of acetyl-CoA formation from various precursors (i.e. glucose and ketone bodies) is the mitochondrion, it may be expected that the formation and subsequent transport of the acetyl-CoA to the cytosol would play an important role in regulation of processes such as acetylcholine synthesis. In this context, therefore, it is the overall objective of this proposal to identify and characterize the mechanism(s) involved in regulating the supply of the acetyl moiety for acetylcholine synthesis. Initially, studies will be performed to determine the contribution of glucose, and ketone bodies as acetyl group precursors in the adult rat brain, and the immature developing rat brain. These studies will indicate the preference for glucose and ketone bodies as acetylcholine precursors in (a) the adult brain explosed to appreciable levels of ketone bodies and (b) in the immature brain at various stages of development. Furthermore, these studies will identify the period of brain development most vulnerable to damage during stress (eg. hypoglycemia). Additional studies will identify and characterize the contribution of the various acetyl group "carriers" involved in the transport of intramitochondrial acetyl-CoA to the cytosol for acetylcholine synthesis. These experiments, conducted under various well defined metabolic state transitions (hypoxia and depolarization) will indicate if acetylcholine synthesis is primarily regulated at the level of acetyl-CoA production or acetyl group transport from mitochondria to cytosol. One of a variety of aims of this proposal is to assess the significance of the entirely cytosolic pathway of acetylcholine synthesis from acetoacetate. If this pathway is of importance then administration of acetoacetate during hypoxia may be of potential therapeutic significance since re-establishment of the depressed rate of acetylcholine synthesis (a consequence of decreased oxidative metabolism of glucose or Beta-hydroxybutyrate) may ameliorate the impairment of behavioral symptoms associated with cerebral hypoxia. Studies described in this proposal may also indicate if the acetylcholine synthetic process is less vulnerable to hypoxia in the adult ketotic rat brain as compared to the normal adult brain. These studies may identify the period of brain development during which the acetylcholine synthetic process is most vulnerable hypoxia.